Very numerous: Fermanagh & Ulster generally, Dublin, South East, Mid-West. Ir. Mac Braoin, a sept of Kilkenny and Ó Braoin, septs of the Midlands & Roscommon.This name occurs as O'Brien and Bruen in some areas. Braon, an early personal name. IF.

Very numerous: all areas, most in Munster and Leinster. Ir. Ó Briain. Leading sept of Thomond (Clare-Limerick), owing prominence to Brian Boru, High-King 1002-1014 A.D. The first name Brian is an old Celtic one, meaning perhaps "noble". GPN.